Wouldnt it
be Great if we Never had to Experience Hunger or Thirst? (Be careful what you
wish for!!)

By Dr. Howard Glicksman

My first recollection of having to really listen to my body occurred when I
was about five or six years old. I had just learned to swim and I really enjoyed
trying to stay under water longer than my friends. But although I could resist
the urge to come up for air a bit longer each time, invariably the need to breathe
would become uncontrollable and Id have to give in. What seemed so weird
about all of this was that it was so easy to resist hunger or thirst when I
was out playing all afternoon and I didnt experience any ill effects doing
so. But this breathing thing certainly got my attention.

Now, as a physician, I am aware of the necessity for all three of these urges
and how and why they are generated in the body in order for us to survive. In
fact, without any one of the inherent drives for air, water or food, we wouldnt
be able to live here on Earth. We could stop right here and ask those who believe
in the step by step development of life; which of these urges occurred first
while still allowing for a multi-system organism with a complicated body plan
to survive without the other two? Still not convinced of the improbability of
macroevolution to explain the development of life as we know it?

Well maybe a better understanding of how the body is able to signal us to
breathe, drink and eat will help you to see what Im driving at here. I
want you to notice that not only are these systems irreducibly complex, but
also each one is absolutely necessary for preventing us from irreversibly damaging
our bodies and causing death. Without the urge to breathe, drink and eat, we
would be unaware of impending injury resulting in our inability to survive and
propagate.

Most people are familiar with how the car works and runs efficiently. Without
gas for the engine to provide energy for locomotion, oil for lubrication of
the many metal parts that are prone to heat-up from friction, and anti-freeze
in the cooling system to prevent the entire system from overheating, the car
can not function. Indeed, the need for gas, oil and anti-freeze within the car
engine is so important that there are gauges readily present on the dashboard
of every car specifically designed to notify the driver if there is any deficiency
in the quantities or function of these vital components. In general, the driver
can only be aware of a possible problem if one of these gauges warns him. If
he ignores these signals it is highly likely that the car will malfunction due
to the lack of gas, seizing of the engine, or overheating.

In a similar fashion, the urges to breathe, drink and eat accomplish the same
thing for our survival. We may ignore them at our own peril, and depending on
the circumstances, run the risk of causing irreversible damage and dying within
minutes to several days or weeks. Unless one is capable of constantly analyzing
the content of oxygen, water and sugar in ones body, while at the same
time knowing how to go about correcting it properly, then one is totally dependent
on the signals that tell us to breathe, drink and eat.

I doubt that there is anyone in the world who would hazard to guess that the
car, with its sophisticated gauges to notify the driver of something going awry,
could possibly have come into existence by the random forces of nature. Yet,
those who rightly present the existence of these more complicated mechanisms
that exist within our own bodies to prevent irreversible damage and death, as
seeming to fly in the face of the validity of macroevolution, are for some reason
viewed by some to be unscientific. Well, lets use medical sciences
current understanding of how the body accomplishes these feats before we try
to pass judgment.

Well review why the body needs oxygen, water and sugar while at the
same time outlining the consequences of failing to provide an adequate supply
to the cells. Then well review how the body is able to monitor its supplies
of oxygen, water and sugar, alert itself when in need, and accomplish the task
of replenishing itself. Finally, well consider what clinical experience
tells us will happen when any of these signaling systems fail.

Your job, throughout this exercise, is to ask yourself exactly how each of
these incredibly complex, interdependent biomolecular and organic systems, could
have developed one step at a time while still allowing for an organism to survive,
given our understanding of the absolute necessity of oxygen, water and sugar
for human cellular function. Dont forget, that if you come up with a logical
explanation for the step by step development of any one of these three systems,
to make macroevolutionary theory stick, youll still need to ascertain
which system existed first before the other two while still allowing the organism
to survive and propagate.

Oxygen and Breathing Everyone seems to be aware of the fact that without oxygen we cannot survive.
But why exactly is this the case? Have you ever wondered what oxygen actually
does in order to allow us to live? Remember, our bodies consist of hundreds
of trillions of cells each of which are surrounded by a cell membrane. This
membrane is able to separate the contents of the cell from the rest of the world
otherwise it would die. In order for the cell to be able to maintain its own
environment and still be able to perform a function in the body it requires
energy.

This energy is harnessed by breaking down sugars, fats and proteins and applying
oxygen to obtain little packets of energy for the cells use. This process
is called oxidative phosphorylation. The molecular by-products of this
process are water and carbon dioxide. In addition, if no oxygen is available,
the cell is capable of providing itself with a lot less energy by using a different
chemical pathway which results in the formation of lactic acid. A build up of
either carbon dioxide or lactic acid in the body can be deadly. Both of these
molecules in the bloodstream tend to make it more acidic, (increase in hydrogen
ion in the blood) which if allowed to build up can have profound negative effects
on cellular function and survival.

The lesson to remember here is that without adequate supplies of oxygen, human
cells cannot function properly. More importantly, well soon see that there
are certain vital cells in the body that are more sensitive than others to the
effects of low or totally absent oxygen. Can you guess which ones?

Most of the time were not consciously aware of our breathing. The body
maintains a rhythmic cycle that allows us to breathe even while we are asleep.
It does this by having a respiratory center located in the medulla of the brain.
This center receives messages from higher levels of the brain which allows us
to voluntarily control our respiration.

But it also receives messages from peripheral and central chemoreceptors which
can tell it what is happening in the bloodstream.

The peripheral chemoreceptors are located in the carotid bodies which consist
of nervous tissue that lies near the carotid vessels. They are sensitive to
arterial blood levels of oxygen, carbon dioxide and hydrogen ion and they send
messages to the respiratory center. But its the central chemoreceptors
which seem to have a stronger effect on the respiratory center. Located in the
brainstem, the central chemoreceptors are able to monitor the changing levels
of free hydrogen ions caused by dissolved carbon dioxide in the cerebral spinal
fluid which bathes the brain. Any combination of a drop in oxygen or an elevation
of carbon dioxide and hydrogen ions in the blood will cause the respiratory
center to be stimulated.

The respiratory center sends out nerve impulses to the muscles of respiration
which move the lungs in and out like a bellows. This causes air to be sucked
in through the nose and mouth, down ever-decreasing caliber airways to the alveoli
in the lungs where oxygen is transferred into the blood and carbon dioxide is
released. The lungs then exhale and push this new mixture of air, containing
less oxygen and more carbon dioxide, out of the body. Once the oxygen has entered
the pulmonary circulation, it hurtles its way to the left side of the heart
where it is then propelled through ever-decreasing caliber vessels to the capillary.
It is here that the oxygen molecule is able to reach its final destination in
the cell where it can be used in the production of energy.

The most sensitive cells in the body to low oxygen and elevated carbon dioxide
levels are the brain cells. How do we know this? Well, up until about 40 years
ago the final common pathway to death was due to cardiopulmonary arrest. This
would happen if your heart stopped or your breathing stopped or they both stopped
simultaneously. It didnt matter what the underlying cause was; a heart
attack, a stroke, pneumonia, or a car accident. Once a person suffered a persistent
cardiopulmonary arrest; they were dead. But with the advent of advanced CPR
techniques, defibrillators, ventilators and medications for pressure support,
sometimes a person can be brought back to life. However, what we have found
is that often after one of these events, even if all of the organ systems are
in apparently good working order, it is often the brain that suffers significant
damage, sometimes to the point of brain death (a term that has only come
into existence in the last 40 years).

Although the brain performs no mechanical work, in order to perform its functions
it requires large amounts of oxygen and energy sources like glucose. But unlike
heart and other muscle tissue, the brain does not store up for itself high energy
sources that may be tapped if the need arises and it is exquisitely sensitive
to low oxygen levels. The brain therefore relies on its large and consistently
controlled blood supply for its immediate energy needs. So if a person suffers
a cardiopulmonary arrest, in which there is no flow of blood to the brain (or
anywhere else for that matter), their brain cells are particularly at high risk
of death within a few short minutes. This occurs because of the lack of readily
available oxygen, energy sources such as glucose, and a subsequent build-up
of carbon dioxide and hydrogen ion levels. In this setting, the energy dependent
membrane mechanisms that are responsible for preserving the integrity of the
brain cells begin to malfunction and soon afterwards the brain cells die.

The reason why you need to understand this is because the respiratory center
itself is part of the brain and therefore is also highly susceptible to being
destroyed in this situation. In fact, one of the criteria for determining that
a patient is indeed brain dead is to expose them to a high concentration of
carbon dioxide to see if that stimulates the respiratory center to make them
breathe. The paradox here being that the respiratory center functions properly
for the body by being sensitive to drops in oxygen and elevations in carbon
dioxide and hydrogen ions in the bloodstream in order that it may start the
process of respiration which directly impacts these blood levels. But the respiratory
center itself consists of cells being one of the most vulnerable in the body
to these same chemical changes. i.e. if the respiratory center doesnt
do its job, it will be one of the first cells in the body to die.

If you review how we are able to maintain the proper levels of oxygen and
carbon dioxide in the bloodstream to meet the demands of the body, youll
see that the entire system is irreducibly complex. Lack of oxygen impacts cellular
function due to the reduction in energy. But elevated carbon dioxide levels
which cause a release of hydrogen ions, i.e. acidosis, also results in cellular
dysfunction and death. In fact, many times for patients who are at immediate
risk of cardiopulmonary arrest due to impending respiratory or metabolic failure,
it is in fact the negative effects of elevated carbon dioxide and/or lactic
acid with their attendant acidosis that causes more damage to cells than a low
oxygen level. The point being that not only oxygen but also carbon dioxide and
hydrogen ions need to be controlled in the body. The respiratory center is sensitive
to changes in all three of these chemicals and by stimulating the lungs is able
to have a direct impact on body survival.

In summary then for oxygen and breathing:

Cellular function is dependent on an adequate supply of oxygen and an efficient
way of ridding itself of carbon dioxide

Both a low level or absence of oxygen and a high level of carbon dioxide
are deadly to human cells

In order that the body can control the levels of oxygen and carbon dioxide
in the blood it has peripheral and central sensors that are able to detect
these molecules

These sensors send signals to the respiratory center in the medulla of the
brainstem based on these levels

The respiratory center sends signals through the nervous system, based on
its combined stimulation from the chemoreceptors, to the muscles of respiration
which causes the rhythmic motion of lung inspiration and expiration

This action results in oxygen being taken from the outside air and being
transferred into the bloodstream while carbon dioxide from within the bloodstream
is transferred out of the body

This newly oxygenated blood travels from the lung to the heart where it
is propelled by the left ventricle throughout the body to all of the tissues

In the tissues the blood travels through capillaries where oxygen can be
unloaded to the tissues and carbon dioxide can be released

The oxygen then goes into the cell where it is used for energy which results
in the production of carbon dioxide that is eventually expelled from the cell
back into the bloodstream and out through the lung

Lung and heart tissue, as well as the muscles of respiration, are themselves
dependent on this system in order to obtain adequate supplies of oxygen and
the release of carbon dioxide

There is ample clinical evidence to show that the respiratory center within
the medulla of the brain is absolutely necessary for survival

The entire system as described above is irreducibly complex in that if one
component is missing or non-functional, the entire system will breakdown and
the body will die. It also demonstrates specified complexity in that the changes
in levels of mere chemicals actually means something to the chemoreceptor cells
which then send a meaningful message to the respiratory center. Macroevolutionists
must be able to come up with a reasonable explanation of how this system could
have developed one step at a time for a multi-system organism with a complex
body plan while still remaining functional.

Water and ThirstWater is absolutely necessary for cellular function. Cells largely consist
of water and their ability to adjust chemical concentrations within their interior
environment is related to their ability to maintain an adequate supply of water.
However, the body is not a closed system for water. It is constantly losing
water through respiration, perspiration, urination and defecation. Although
the cellular process for energy production does yield some water molecules,
the amount is not enough to compensate for this continuous loss. If this water
is not replaced in a timely fashion, then over several days the body can become
dehydrated and die.

What this means on the cellular level is that as the body loses more and more
fluid, this will force water out of the cells into the bloodstream to try to
maintain a proper blood volume and blood flow. This motion of water out of the
cells will cause them to shrink in size and eventually chemical imbalances will
arise within the cell that overwhelms the cells ability to cope and it
will die. On a body level, this drop in the global supply of water will cause
a drop in total blood volume and blood flow which if not corrected will overwhelm
the bodys compensatory mechanisms and will result in a serious drop in
blood pressure, shock and death. In order to prevent this from happening it
is absolutely necessary that the body take in water. But how much and how often?
Not to worry, for the body has a system that appears to be specifically designed
to keep the water balance steady in order to prevent excessive cell shrinkage,
loss of effective blood volume, and consequently cell and total body death.

Remember we said that the first thing that happens when the body needs water
is for the cells to shrink a little as they supply water to the circulation.
In the hypothalamus there are osmoreceptor cells that are specifically sensitive
to cell shrinkage and therefore are capable of gauging the water needs of the
body. Based on the amount of shrinkage that they experience, these osmoreceptor
cells send signals to other nearby cells which release a hormone called vasopressin
into the bloodstream. This hormone travels to the kidney where it prompts
it to reabsorb more water from the urine that is currently in production. But
in addition, it also appears that vasopressin directly affects the thirst center
that is located in the hypothalamus, which tells the body that it needs to take
in some water. (For a more detailed description of this process and its own
inherent questions for macroevolutionists please see my column He Who Cannot Control
His Water Will Not Survive)

Remember that dehydration affects the body by reducing the total blood volume
and blood flow which if left unchecked will result in a lowering of the blood
pressure, shock and death. Within the kidney exists a sensory cell that is able
to monitor renal blood flow. Significant drops in this parameter will cause
this cell to secrete a hormone called renin. The renin enters the bloodstream
which after a cascade of molecular reactions results in the formation of a hormone
called angiotensin II which basically does three things to try to solve
the situation. First, it tightens the muscles around small arterioles to try
to raise the blood pressure. Second, it causes the adrenal gland to secrete
a hormone called aldosterone which stimulates the kidney to hold onto
more sodium and water. And finally, angiotensin II stimulates the thirst center
in the hypothalamus which tells the body that it needs to take in some water.
(For a more detailed description of this process with its inherent questions
for macroevolutionist please see my column Life on Earth is Definitely
not for the Faint-Hearted).

Once the thirst center sends out the alarm, the body makes a conscious effort
to try to drink some water if possible. It does this by a complicated neuromuscular
system that is able to activate certain sensory and motor devices in the body
to seek out, obtain and drink fluids. Once the water has been deposited in the
mouth and propelled down the esophagus into the stomach it is rapidly absorbed
into the body and enters the circulation.

The replenished circulation then travels throughout the body and restores the
water that is needed in the cells. The slaking of ones thirst is like
all of the cells of the body heaving a large collective sigh of relief. Moreover,
the combination of an adequately restored cell size and blood volume results
in a reduction in the secretion of both vasopressin and renin. And so the cycle
begins again!

Diseases and conditions affecting the thirst center are very rare. But they
are known to occur, often due to very localized injuries or diseases of the
hypothalamus. These people are very prone to fluid and chemical imbalances which
can result in severe debility and death. Quite often if they are very careful,
make sure that they dont overdo it, and take in enough water, particularly
in hot weather, they can survive. However, it is only through the knowledge
of modern medical science that these people can be instructed and advised about
how to live their lives given their functional abnormalities.

Without a thirst center, it is evident that any multi-system organism with
a complex body plan that is dependent on tight control of its internal water
supply for survival; wouldnt!

In summary then for water and thirst:

Cellular, and consequently, body survival is dependent on water

In order that the body may maintain an adequate supply of water it has at
least two very important systems which are activated by changes in water supply
within the cell and the body as a whole

One system monitors cell shrinkage and is able to stimulate the secretion
of a hormone that helps the body to hold onto more water while at the same
time telling the thirst center to tell the body to drink water

Another system monitors renal blood flow which results in the secretion
of a hormone that is capable of activating other biomolecules which also results
in the body being able to hold onto more water and stimulating the thirst
center to tell the body to drink water

The thirst center then notifies the conscious mind of the body to seek out,
obtain, and drink water through various neuromuscular means

The gastrointestinal tract absorbs the ingested water where it is able to
replenish the circulation and through it the cells of the body

Clinical evidence exists to show that without the thirst center, the body
would not be able to survive

This system for water balance, like the bodys system for controlling
blood oxygen and carbon dioxide described beforehand, demonstrates both irreducible
and specified complexity in that if one component is missing or not functioning
properly, the entire system will breakdown and that mere changes in cell size
and blood flow have meaning to particular cells in the body. Macroevolutionists
must be able to come up with a reasonable explanation of how this system could
have developed one step at a time for a multi-system organism with a complex
body plan while still remaining functional.

Food and HungerEveryone is familiar with the fact that without food we would die. Basically,
food contains carbohydrates, proteins, fats, minerals and vitamins. These components
are necessary for the structural and metabolic needs of the body. Therefore,
it is possible to say that we literally are what we eat! However for the purposes
of this discussion we will be focusing on how food provides the substrate, usually
glucose and other molecules, for cellular energy in the body.

When the body does not take in enough calories to make up for its energy needs
it is able to tap into various sources to take up the slack. The muscle and
liver contain glycogen which is a storage complex consisting of glucose molecules.
The body can also use its fat stores which contain lipids, and if necessary
even proteins can be broken down and used for energy as well. So as you can
see, if one has no intake of food, it will take some time before the energy
needs of the body are severely compromised to result in death. In fact we are
talking in the order of many weeks. The actual mechanism for death in starvation
is poorly understood but it usually occurs due to infection because the bodys
ability to defend itself is compromised. Another contributing factor is that
oftentimes when faced with less and less substrate to use for energy, the body
will opt to use a chemical reaction that ultimately results in the build-up
of hydrogen ions in the bloodstream (acidosis) which results in cellular dysfunction
and ultimately death.

The bodys ability to notify itself that it needs to eat is a very complicated
process that is still undergoing investigation. In the hypothalamus there is
a hunger center that motivates the body to eat, and a satiety center which tells
the body to not eat. Both of these centers are stimulated by various hormones
and signals that derive from food intake, its metabolism and the organs involved
in both of these processes.

Once the hunger center notifies the body of the need to eat, if it decides
to act on the signal it will use the neuromuscular system to seek out, obtain,
and eat food. The food will be placed in the mouth where it will be tasted by
the tongue and mixed with saliva as it is chewed. Eventually it will be sent
down the esophagus into the stomach to continue the process of digestion. Within
the stomach and the small intestine the food will be exposed to fluids that
contain various chemicals and enzymes that allow the body to absorb the sugars,
fats, proteins, minerals and vitamins that come its way.

Once digested and absorbed into the body, these molecules will enter the bloodstream
and be distributed to where the body needs them. As this process occurs, various
hormonal and nerve mediated signals will be transmitted in a feedback loop to
the hypothalamus which will cause the hunger centers message to turn off
for the time being. As the hunger urge becomes satisfied, all will be calm again!

Regarding the absolute necessity of the hunger and satiety center; studies
in rats have clearly shown that destruction of the hunger center results in
aphagia (lack of eating) which leads to starvation and death. And destruction
of the satiety center results in hyperphagia (overeating) which leads
to severe obesity and dysfunction.

Once again, it is evident that all of the components that are necessary for
the body to be able to obtain, process and distribute the nutrients needed for
its survival are all wrapped up in an irreducible and specified complex system.
The mandate presented to macroevolutionists, who believe in the step by step
development of life as we know it, should be to explain how this system came
about in a multi-system organism with a complex body plan while allowing it
to survive.

In conclusion, it is evident that all three of the inner drives that we have
for breathing, drinking and eating are absolutely necessary for our survival
here on Earth. But each nerve center itself is incapable of accomplishing the
incredibly complicated task of providing the necessities of life. Below is a
summary of the components required for each system to work:

A signaling system involving various sensors activated by specific
chemicals, cell status, or body function, which results in the release of
messenger chemicals or signals:

A nerve center within the body that receives these signals of variable
strength and sends out an equally variable message to tell the body to perform
a specific function that will ultimately affect the messages that the nerve
center is receiving:

Breathing: respiratory center

Drinking: thirst center

Eating: hunger and satiety centers

An organ system that is able to be activated by the nerve center
to accomplish the function for which the signaling system is intended:

Breathing: Neuromuscular system activates muscles of respiration which
allows for lung function

Drinking: Neuromuscular system activates appropriate muscles and sensory
devices to allow organism to detect, procure, and drink water which, enters
the gastrointestinal tract where it is absorbed into the bloodstream

Eating: Neuromuscular system activates appropriate muscles and sensory
devices to allow organism to detect, procure and eat food, which enters the
gastrointestinal tract where it is digested and absorbed into the circulation

Review of these systems shows that without each component the entire system
would malfunction and death would occur. Macroevolutionists must somehow be
able to explain how each of these systems could have developed one step at a
time while at the same time allowing for a multi-system organism with a complex
body plan to survive and propagate. Included in this analysis must be an explanation
of which of these vital nerve centers (respiration, thirst, hunger) came on
the scene first and how the organism was able to survive without the other two.

The mere existence of similar systems within similar organisms does not necessarily
prove that all of this came about by the random forces of nature. It only shows
that these organisms are subject to the same laws of nature and therefore one
would expect similar means to be used to produce similar biomolecular devices
and organs for life on Earth.

I am unaware of anyone who is currently proposing that because the blueprints
and the machinery that is used in the making of the parts and production of
different gasoline

powered vehicles are very similar, that they therefore all came into being
by the random forces of nature. The fact that there are similar looking components
in similar looking systems appears to be the only evidence that supports the
theory of macroevolution as it is currently being taught. However, it is equally
important to advise students of the apparent weaknesses of this theory given
our understanding of how biological systems actually function and survive. I
have attempted here to provide some questions that I think need definitive answers
before macroevolution can be accepted as a well-proven fact. Does intelligent
design fill the void? You be the judge!

Next month well look at how the body reconciles with the fact that oxygen
does not dissolve well in blood, but nevertheless, it still needs to get enough
of it to the tissues for us to survive. Join me in: Why Blood is Red and
other Bedtime Stories (Count Dracula would have been so disappointed). Questions
or comments about this or any other column are welcomed at drhglicksman@yahoo.com.

Dr. G.

Howard Glicksman M. D. graduated from the University of Toronto
in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario
and Spring Hill, Florida. He recently left his private practice and has started
to practice palliative medicine for a Hospice organization in his community.
He has a special interest in how the ethos of our culture has been influenced
by modern sciences understanding and promotion of what it means to be
a human being.